This invention relates to a method of making a eutectic mixture of copper and tricopper phosphide by the reaction of phosphine with elemental copper.
Copper phosphide, Cu.sub.3 P.sub.2, and tricopper phosphide, Cu.sub.3 P, are used as a source of copper and phosphorus in making alloys of steel, bronze, and other metals. The only process currently employed to produce the copper phosphides is a batch process which involves directly combining elemental phosphorus and molten copper. This operation is dangerous due to the use of elemental phosphorus, which is not only toxic, but can ignite spontaneously upon contact with air.
There are other sources of phosphorus, such as phosphorus contaminated sludge, but phosphorus from those sources has not been commercially utilized in making copper phosphide. Indeed, in elemental phosphorus production, phosphorus contaminated sludge is regarded as a valueless by-product and the phosphorus in it is a dangerous contaminant that can become an environmental pollutant. In elemental phosphorus production a stable emulsion of phosphorus, water, and dirt is produced which contains elemental phosphorus. Since the elemental phosphorus is under water, it is not oxidized and remains as elemental phosphorus. While this sludge can be stored in ponds, it is very toxic, and, if it escapes into the environment and seeps into streams, it can kill fish at extremely low concentrations. The phosphorus can be removed from the sludge by a costly energy intensive processing involving evaporation of both the water and the phosphorus at temperatures of over 300.degree. C. At high phosphorus concentrations this may be economical, but a low phosphorus levels evaporation is extremely unattractive. Thus, at low concentrations (e.g., 10% or less) the phosphorus in the sludge only adds to the expense of the industrial process producing the sludge, though it would be valuable if it could be used to make copper phosphide.